Directional drilling machines are used to drill holes along a generally horizontal path beneath the ground. After a hole is drilled, a length of cable or the like can be passed through the hole. Such directional drilling machines eliminate the need for digging a long trench to lay a length of cable or the like.
A typical directional drilling machine includes an elongated track that can be aligned at an inclined orientation relative to the ground. A drive head is mounted on the track so as to be moveable along the length of the track. The drive head includes a drive member that is rotated about a drive axis that is generally parallel to the track. The drive member is adapted for connection to a length of pipe. For example, the drive member can include a threaded end having either female or male threads.
To drill a hole using the directional drilling machine, the track is oriented at an inclined angle relative to the ground, and the drive head is retracted to an upper end of the track. Next, a length of pipe is unloaded from a magazine and is coupled to the drive member of the drive head. Once the pipe is connected to the drive head, the drive head is driven in a downward direction along the inclined track. As the drive head is driven downward, the drive member is concurrently rotated about the drive axis. Typically, a cutting element is mounted at the distal end of the pipe. Consequently, as the drive head is driven down the track, the rotating pipe is pushed into the ground thereby causing the pipe to drill or bore a hole. By stringing multiple pipes together, it is possible to drill holes having relatively long lengths.
After drilling a hole, it is common for a back reamer to be connected to the end of the drill string. Once the back reamer is connected to the end of the drill string, the directional drilling apparatus is used to pull the string of pipes back toward the drilling machine. As the string of pipes is pulled back toward the drilling machine, the reamer enlarges the pre-drilled hole, and the pipes are individually uncoupled from the drill string and loaded back into the magazine of the directional drilling machine.
To enhance drilling productivity, it is important to maximize the efficiency in which pipes can be loaded into and unloaded from the magazine of a directional drilling machine. Until fairly recently, pipes were manually carried between the magazine and the drive head of a drilling machine, and were also manually loaded into and unloaded from the magazine. Recent developments have improved pipe loading and unloading efficiencies through automation. For example, U.S. Pat. No. 5,556,253 to Rozendaal et al. (the '253 patent), and U.S. Pat. No. 5,607,280 (the '280 patent) to Rozendaal, disclose improved pipe loading/unloading devices. The '253 and '280 patents disclose devices that effectively use gravity to automatically unload pipes from a magazine. The '253 and '280 patents also disclose devices each having pipe transfer members that automatically move pipes between a magazine and a drive head. The advances provided by the devices disclosed in the '253 and '280 patents have assisted in significantly improving a drill operator's ability to enhance drilling productivity.